1. Field of the Invention
The present invention relates to a device for detecting misfire of an internal combustion engine.
2. Description of the Prior Art
A known device for detecting misfire of an internal combustion engine due to failure of ignition, etc. is adapted to diagnose misfire on the basis of a variation of crankshaft rotational speed during combustion strokes of each cylinders.
A problem of the prior art device is that the measurement phases or periods for measurement of crankshaft rotational speed at each cylinders are not constant but liable to vary with respect to the cycle of operations of the engine, resulting in a difficulty of attaining an accurate diagnosis of misfire.
Another problem is that a variation of crankshaft rotational speed which is caused by disturbance, e.g., which may possibly be caused by an impact transferred from the road wheels to the drive train when the vehicle is running on a rough road, is erroneously judged as occurrence of misfire at one cylinder or a plurality of cylinders.